Original Paper

European Food Research and Technology

, Volume 227, Issue 1, pp 83-92

Influence of the degree of polymerisation in the ability of catechins to act as anthocyanin copigments

  • S. González-ManzanoAffiliated withGrupo de Investigación en Polifenoles, Facultad de Farmacia, Universidad de Salamanca, Unidad de Nutrición y Bromatología
  • , N. MateusAffiliated withCentro de Investigação em Química, Departamento de Química, Faculdade de Ciências, Universidade do Porto
  • , V. de FreitasAffiliated withCentro de Investigação em Química, Departamento de Química, Faculdade de Ciências, Universidade do Porto
  • , C. Santos-BuelgaAffiliated withGrupo de Investigación en Polifenoles, Facultad de Farmacia, Universidad de Salamanca, Unidad de Nutrición y Bromatología Email author 

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Abstract

The objective of this study was to evaluate the influence of the degree of polymerisation of flavanols in their ability to act as anthocyanin copigments. With this aim, ethyl-bridged catechin derivatives were produced by reaction between catechin and acetaldehyde. Further fractionation in Toyopearl HW-40 allowed the separation of five fractions of increasing molecular size containing mixtures of compounds in the range from monomers to hexamers as established by LC-MS. The copigmentation assays were carried out in citrate-phosphate buffer solutions in 12% ethanol at pH 3.6, using malvidin 3-O-glucoside as pigment and increasing concentrations of the different catechin fractions to obtain copigment to pigment ratios ranging 0:1–20:1. Copigmentation was assessed from the modifications in the visible spectra of the solutions; chromatic analysis in the CIELAB colour space was used to characterise the copigmentation effect. It was found that all the compounds assayed were able to interact with the anthocyanin and induced changes in the colour of the solutions. The greatest effect was induced by oligomers containing 2–3 elementary catechin units, whereas monomers were the poorest anthocyanin copigments among the compounds checked. An interesting observation was that the formation of the copigmentation complexes was not and immediate process, but it required some time to attain the equilibrium, suggesting that the phenomenon was controlled thermodynamically rather than kinetically.

Keywords

Ethyl-bridged oligomers Catechin Malvidin 3-O-glucoside Copigmentation Colour Tristimulus colorimetry